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Home >> Chevrolet >> 1998 >> Astro Van Cargo, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0121 - TP Sensor System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Turn ignition on, engine off. Using scan tool, read TP ANGLE value. If value is greater than 2 percent, go to step 4). If value is not greater than 2 percent, go to next step.
  3. Observe scan tool while moving throttle from closed to wide open, and closed again. If TP ANGLE value is greater than 2 percent, go to next step. If value is 2 percent or less, go to step 5).
  4. Disconnect TP sensor harness connector. If TP ANGLE value is zero percent, go to step 6). If value is not zero percent, go to step 9).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, go to DIAGNOSTIC AIDS.
  6. Check for faulty connection at TP sensor. Repair as necessary. After repairs, go to next step. If connection is okay, go to step 8).
  7. Repair circuit as necessary. After repairs, go to step 10).
  8. Replace TP sensor. After replacing sensor, go to step 10).
  9. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set DTC. If scan tool indicates that this DTC RAN AND PASSED, go to next step. If scan tool does not indicate that this DTC RAN AND PASSED, repeat step 2).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.
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